This invention relates to certain novel 3-alkyl-5-(alkoxy- or alkylthio-phosphynyl or phosphinothioylthiomethyl)-1,2,4-oxadiazoles and their use as soil insecticides to combat corn root worm. In particular I have found that the compounds of this invention show surprisingly good activity in killing Diabrotica larvae.
German Offenlegungschrift No. 2,919,621 discloses insecticidal compounds of the general formula: ##STR2## wherein X is oxygen or sulfur; R.sub.1 is hydrogen, C.sub.1 to C.sub.4 alkyl optionally substituted with halogen, C.sub.1 to C.sub.3 alkoxy, or phenyl; R.sub.2 is C.sub.1 to C.sub.4 alkyl; and R.sub.3 is C.sub.1 to C.sub.4 alkyl, C.sub.1 to C.sub.6 alkylamino, allylamino or di-(C.sub.1 to C.sub.3) alkylamino where the two alkyl groups on the nitrogen may form a 5- or 6-membered ring which optionally may contain an oxygen atom.
The compounds of the German Offenlegungschrift were disclosed as effective against "sucking" and "biting" insects as well as mites and ticks of the order Acarina. The examples showed testing certain of the compounds for insecticidal activity on red spider mites, bean aphids, houseflies, German cockroach, Mexican bean beetle larvae, corn beetle larvae, flour weevils and African boll weevil larvae.
Commonly-assigned, U.S. Pat. No. 4,237,121 discloses the use of corn root worm insecticides of compounds of the formula: ##STR3## wherein X, Y, Z and V are sulfur or oxygen and R.sup.1, R.sup.2, R.sup.3 are alkyl of 1 to 4 carbon atoms.
Commonly-assigned U.S. Pat. No. 4,213,973 discloses the use of compounds of the formula ##STR4## wherein X, Y, Z and V are oxygen or sulfur; R.sub.1 is hydrogen or alkyl of 1 to 6 carbon atoms and R.sup.2 and R.sup.3 are alkyl of 1 to 6 carbon atoms, as corn root worm insecticides.
U.S. Pat. No. 3,432,519 discloses insecticidal and acaricidal compounds of the general formula ##STR5## wherein R represents a hydrogen atom, an alkyl group containing 1 to 6 carbon atoms optionally carrying an alkoxy substituent containing 1 to 4 carbon atoms or an aryl group (preferably phenyl) which may carry one or more substituents selected from hydrogen atoms, the nitro group and alkyl, alkoxy and alkylthio groups containing 1 to 4 carbon atoms, R.sub.1 represents a hydrogen atom or an alkyl group containing 1 to 4 carbon atms, R.sub.2 represents an alkyl group containing 1 to 4 carbon atoms and X represents an oxygen or sulfur atom.
British Pat. No. 1,213,707 discloses insecticidal compounds of the general formula ##STR6## wherein X.sub.1 and X.sub.2 which may be the same or different, each represents an oxygen or sulfur atom; A represents an alkylene group; R.sub.1 represents an alkyl group, R.sub.2 represents an alkyl or alkoxy group; and R.sub.3 represents a hydrogen atom or an optionally substituted carbamoyl or amino group.
The examples of the British patent show testing of certain of the compounds for insecticidal activity on adult houseflies; mosquito larvae, diamond back moth larvae, aphids and adult mustard beetles; red spider mites; and white butterfly larvae. None of these tests involved application and use of the insecticide in the soil habitat of the insects.
U.S. Pat. No. 4,028,377 discloses insecticidal compounds of the general formula: ##STR7## wherein R.sub.1 represents hydrogen, unsubstituted alkyl, benzyl or phenyl, R.sub.2 represents methyl or ethyl, and R.sub.3 represents unsubstituted C.sub.1 -C.sub.7 alkyl optionally interrupted by oxygen or represents C.sub.3 -C.sub.4 alkenyl.
The examples of the U.S. Pat. No. 4,028,377 show testing of certain of the compounds for insecticidal activity on ticks in cotton wool; larvae of ticks; mites; and on root-gall-nematodes in soil. In the latter test, the soil infested with the root-gall-nematodes was treated with the compounds to be tested and then tomato seedlings were planted either immediately after the soil preparation or after 8 days waiting.
British Pat. No. 1,261,158 discloses compounds of the general formula: ##STR8## wherein R.sub.1 represents an alkyl group, R.sub.2 represents an alkyl or alkoxy group, X represents an oxygen or sulfur atom; A represents a saturated divalent aliphatic hydrocarbyl group; Y represents a halogen atom or an alkyl or alkoxy carbonyl group; and n is 0, 1 or 2. The compounds of the examples of British Pat. No. 1,261,158 were tested for insecticidal effectiveness on flies, mosquito larvae, moth larvae, mustard beetles, aphids, spider mites and butterfly larvae.
As described in the Ortho Seed Treater Manual, copyright 1976, Chevron Chemical Company, page 27, corn root worms have been controlled with chlorinated hydrocarbon insecticides, but in areas where resistance to such treatment has developed, good control has been obtained with organic phosphorus or carbamate soil insecticides such as Diazinon and Carbofuran insecticides. The chemical names and formulas for these latter insecticides are given below: ##STR9##